Positive pressure felt dewatering and cleaning device and method

Abstract

Apparatus and method for dewatering papermaker's felt utilizing positive pressure, the felt being deflected in an arc of at least about 90° but less than about 180° by means of a dewatering shoe with a rounded nose having a radius of from about 2" to about 4", the nose of the shoe having an elongated orifice with an effective width of from about 1" to 4" through which air under pressure is directed into the felt. Low pressure flooding means or high pressure shower means may be mounted in the rounded nose of the shoe in advance of the dewatering orifice to direct a cleaning fluid into the felt in advance of dewatering.

What is claimed is: 
     
       1. A positive pressure dewatering device for papermaker's felts comprising a hollow shoe having a rounded nose adapted to contact and deflect the felt being dewatered, said nose having a radius of from about 2" to about 4" and an arc which is greater than 90° but less than 180°, an elongated lengthwise orifice in said nose having an effective width of from about 1" to about 4", and means within said shoe in communication with said orifice for discharging air under pressure therethrough. 
     
     
       2. The positive pressure dewatering device claimed in claim 1 wherein wear bars extend lengthwise of said orifice at spaced apart intervals. 
     
     
       3. The positive pressure dewatering device claim in claim 1 including applicator means within the nose of said shoe for injecting cleaning fluid into the felt, said applicator means being positioned ahead of said orifice with respect to the direction of travel of the felt about the nose of said shoe. 
     
     
       4. The positive pressure dewatering device claimed in claim 3 wherein said applicator means comprises a low pressure flooding shoe. 
     
     
       5. The positive pressure dewatering device claimed in claim 3 wherein said applicator means comprises high pressure shower means. 
     
     
       6. A method of dewatering papermaker's felts which comprises the steps of moving the felt in a path of travel, deflecting the moving felt in an arc of at least about 90° but less than about 180° by means of a dewatering shoe with a rounded nose having a radius of from about 2" to about 4", and directing air under pressure into said felt through the rounded nose of said shoe at a pressure determined by the formula   P=T/R     wherein P represents pressure in pounds per square inch, wherein T represents felt tension in pounds per linear inch of felt width, and wherein R represents the radius of the rounded nose of the shoe.   
     
     
       7. The method claimed in claim 6 including the step of directing a cleaning fluid into the felt through the rounded nose of the shoe prior to directing air under pressure into the felt.